The present invention relates generally to an apparatus for the separation of liquid suspensions, especially suspensions of cellular material such as blood and blood components. More particularly, the invention relates to a novel integral flow control cassette and separation device for the separation or fractionation of one or more constituents of blood.
Broadly speaking, whole blood is a suspension of red blood cells, white blood cells and platelets in liquid plasma. Separation of one or more of the constituents or components of blood from whole blood or from a suspension comprising fewer than all of the usual blood components is referred to as xe2x80x9capheresis.xe2x80x9d Often, apheresis is carried out at the time of blood collection from a donorxe2x80x94and the collected component is stored for later administration to a patient in need of that blood constituent. Alternatively, apheresis may be used as a therapeutic procedure, wherein the blood component is being withdrawn or depleted as part of the treatment of a patient.
Machines have long been available for automatically processing the blood of donors or patients by withdrawing the desired constituent and returning to the donor or patient the remaining blood components. For example, platelets may be collected from healthy donors and red cells and plasma returned to the donor. Similarly, concentrated red cells may be collected for later transfusion, and platelets and/or plasma returned to the donor. Other procedures may be used for collecting other components, such as plasma or white cells.
Machines for separating blood components, i.e. for performing apheresis, have been based on different operating principles. Centrifugation is one widely-recognized technique, which takes advantage of the slight differences in the density of blood constituents to separate them in a centrifugal field. Commercial apheresis centrifuges include the CS-3000(copyright) and Amicus(copyright) separators sold by Baxter Healthcare Corporation of Deerfield, Ill., and the Spectra(copyright) and Trima(copyright) separators by Cobe Laboratories of Golden, Colo. Other manufacturers of commercial blood separators include Fresenius AG, Germany, and Haemonetics Corporation of Braintree, Mass.
Separation of blood components by use of a filter membrane has also been used. One remarkable advance in blood separation technology using membrane filtration has employed a spinning rotor. More particularly, this technique employs the relative rotation between two concentric members and the generation of Taylor vortices in the gap between the relatively rotating members. In a commercial separator employing the principle, marketed as the Autopheresis C(copyright) separator by Baxter Healthcare Corporation, the separator includes a membrane-covered spinner, having an interior collection system, disposed within a stationary shell. Anticoagulated blood is fed through a radial gap between the spinner and the shell. Taylor vortices are created in the gap by the spinning roter, and provide an interior sweeping motion which tends to clear the membrane of cellular matter that would otherwise deposit on the membrane and clog the pores. As a result of the membrane cleaning, plasma filtrate can be rapidly extracted through the membrane. U.S. Pat. No. 5,194,145, incorporated by reference herein, more specifically describes the construction and operation of this device.
While both the centrifugation and spinning rotor techniques have worked exceptionally well, the equipment employing the techniques is relatively complicated and operators are required to undergo extensive training. For convenience, health, and safety reasons, blood separation or apheresis machines utilize disposable tubing sets and separation chambers for the separation and collection of the various blood components. The disposable tubing set and separation chamber are mounted on a reusable device which controls flow through the tubing set in accordance with an operator-selected procedure or other operator instruction.
The reusable separation device includes pumps, clamps, sensors and monitors to control flow of blood, blood components and other fluids, such as anticoagulant and saline, through the tubing set and associated separation chamber. Accordingly, it is very important that the tubing set be properly mounted on the hardware to assure proper and safe operation. Due to the large number of guides, pumps, clamps, monitors and sensors onto which the tubing must be carefully mounted, set up of these apheresis devices is often time consuming, tedious, and subject to the possibility of human error. The set-up may be further complicated when the tubing set-up or installation procedure varies with the blood component to be collected. As in any task requiring operator involvement, there is a risk, even if very small, of mis-installation of the tubing set. Although such mis-installation does not typically endanger the donor or patient because of built-in safeguards, it may require time consuming and costly replacement of the tubing set or delay while the operator trouble-shoots and corrects the mis-installation.
Of course, complex tubing sets have the added drawback of being expensive to manufacture because of the intensive amount of labor involved, and the increased vigilance required to assure proper assembly.
Steps have been taken to design apheresis tubing sets that are easier and less time consuming to install, and less subject to error. One example of such a system is the Baxter Amicus(copyright) separation system. The Amicus system employs cassettes that are mounted on pump and valving stations on the reusable device, eliminating much of the manual installation of the tubing set. The cassettes have pre-formed passageways that are controlled by the valving stations in accordance with the procedure pre-selected by the operator. An example of this cassette arrangement is disclosed in U.S. Pat. No. 5,462,416, which is incorporated by reference herein.
Although the Amicus system eliminates a significant portion of the tubing set-up steps in the older apheresis devices, it continues to require some mounting steps, as well as assembly of the disposable separation chamber with a reusable centrifuge bowl or chamber in the device. Thus, there continues to be room for more improvement.
In addition to the desire to simplify the tubing set installation procedure, there is a continuing desire to reduce the size and weight of the separation devices. The CS-3000(copyright) and Amicus(copyright) centrifuges, for example, are relatively large roll-about machines. Although the Amicus(copyright) is significantly lighter and easier to move than the CS-3000(copyright), there are many situations where a transportable, such as a small suitcase size, apheresis device would be advantageous. A readily transportable device could have particular application, for example, to blood collection drives which are conducted off-site, at a location away from the main blood bank or hospital laboratory, or to treatment of ill patients who cannot be readily moved and are located where it is not possible to bring a larger apheresis device. Whether the apheresis device is of the conventional size or the transportable type, there remains a need to reduce the possibility for error during the tubing connection process, to reduce or simplify operator training for loading and operation of the equipment, and to reduce manufacturing complexity and cost.
The present invention is generally embodied in a disposable module adapted for cooperative mounting on a reusable device or module for processing a suspension comprising blood or blood components, and in the system including the disposable module and reusable device. In accordance with the present invention, the disposable module includes an integral flow control cassette and separator. The separator includes a rotor rotatably mounted therewithin, and may be based on a centrifugation, membrane separation or such other rotor-based technique or principle as is desired. The flow control cassette includes an inlet for communicating with a suspension source, and the cassette defines a first flow path communicating between the suspension inlet and an inlet in the separator. A separator outlet is provided for removing a separated portion of the suspension, and the cassette defines a second flow path communicating with the separator outlet.
More specifically, the flow control cassette defines a plurality of flow path segments and a plurality of valve stations interconnecting two or more flow path segments to selectively open or close communication between the segments. The valve stations, which in their broader aspects are operable pneumatically, hydraulically, mechanically or otherwise, are cooperative with the reusable module to control fluid flow through the flow path segments and to define the first and second flow paths. An array of flow path segments and valve stations defined within the cassette may, by operation of the reusable hardware, be selectively connected to provided a variety of different fluid flow configurations, depending on the apheresis process requested.
To move fluid through the disposable flow control cassette may also include pre-formed pump stations, also operable pneumatically, hydraulically, mechanically or otherwise, to pump fluid through the flow path defined by flow path segments and valve stations, as configured by the reusable device in response to a control program for a procedure selected by the user. This arrangement eliminates the routing of tubing through or around pump heads, as required on many prior devices. The integral flow control cassette and separator of the present invention provide a particularly compact arrangement. When the separator is based on the spinning rotor membrane separation principle, the entire disposable module and reusable module can be reduced to the size of a small suitcase, which is readily transportable for off-site collection or depletion procedures.
In a more preferred form, the present invention is embodied in a disposable blood separation set, alone and in combination a reusable actuator device having a plurality of pressure actuators responsive to a control program, in which the separation set includes a cassette including pre-formed pressure actuated pump stations, preformed fluid flow path segments and preformed pressure-actuated valve stations. The cassette also includes an integral fluid separation device communicating with fluid path segments and a plurality of cassette ports communicable with the path segments to convey the flow of fluids to and from the cassette and separation device via flow paths created by the pressure actuators selectively changing pressure to the valve and pump stations in response to a control program. The pressure change to actuate the pump or valve stations may be an increase in pressure such as at or above atmospheric pressure (i.e., a positive pressure), or a decrease in pressure such as to at or below atmospheric pressure (i.e., a negative pressure).
The reusable actuator device or module may be programmable for a plurality of different user-selected separation processes, for example collection of plasma or red cell concentrate or other, and the disposable set can preferably accommodate two or more different blood processing procedures. The cassette in the more preferred form lends itself to different procedures due to the plurality of flow path segments interconnected at valve stations so that selective operation of the valve stations by the actuators establishes the different flow paths needed for different procedures.
More specifically, the cassette may include a rigid plastic base and a flexible membrane covering at least one side of the base. The rigid plastic base includes upstanding walls on one side of the cassette defining valve and pump wells. When the cassette is mounted into the actuator device, the flexible membrane is pressed against the edges of the walls to seal each well to define a closed valve or pump station. Actuators in the reusable device or module control the valving and pumping action by changing the increasing or decreasing pressure applied to the outside surface of the membrane overlying the valves and pump chambers. For example, by increasing pressure against the membrane, it may be pressed against a valve port in the valve well to block flow. Similarly, repeated flexing of the membrane into and out of the pump chamber in response to pressure changes by the actuator may be used to pump fluid through the cassette in sequential draw and pump cycles.
Upstanding walls on the other side of the cassette base define a plurality of flow path segments that extend between valves, pumps and/or separator. These walls may be sealed by a rigid plastic cover or by a flexible membrane as with the one side of the cassette. Thus, fluid flow paths may defined in the cassette for different separation procedures in response to the selected control program in the actuator device by selective pressure changes applied to the flexible membrane at the valve stations, and fluid pumped through the cassette as required for the selected procedure. Accordingly, the same cassette may be used for a variety of different procedures with minimum operator setup required and with greatly reduced opportunity for operator error.
These and other features and aspects of the present invention are set forth below in the detailed description of the attached drawings.